All Posts in “Lighting quality”

Tag

In Christopher Alexander’s book A Pattern Language he points out: “When they have a choice, people will always gravitate to those rooms which have light on two sides, and leave the rooms which are lit only from one side unused and empty.” He touts that “this pattern, perhaps more than any other single pattern, determines the success or failure of a room.”

Why is this? Alexander goes on to point out that his experiments had been rather informal and drawn out over many years. But the trend is very real. He also recalls that light on two sides was a tenet of the Beaux-Arts design tradition. What is it about certain patterns of light that attract people or enhance space and volumes effectively? Looking to the past may be the best way to design daylighting for the future.

In last September’s entry, ‘A Daylighting Pattern Language’, Robert Osten used Le Thoronet abbey as an example of how well small apertures were designed for introducing daylight into the interiors of large masonry constructions. Before the use of sophisticated computer models and analytical studies, architects based their designs on common sense, common practice, and a basic understanding of the relationship between architecture and the sun. Why are some spaces much more successful than others? When it comes to light, and especially daylight, it’s a human response: what feels good.

Let’s examine some reasons why a room or space with bilateral light is more successful than one with light only from one side.

The first, seemingly obvious, reason is brightness balance and contrast ratios. For example, sitting in a space and talking to a person in front of a window without the benefit of light on their face (from another window or skylight on the opposite side of the room) is not only uncomfortable, but since their face is in silhouette, it is difficult to read their expression, giving us little or no information about their mood or response.

In work environments, the contrast ratio could cause discomfort, and result in eye fatigue. R. G. Hopkinson in his book Architectural Physics: Lighting, published back in 1963, discusses the issues of glare and contrast in great detail, showing how it affects much more than simply the quantity of light. Today, from simple evaluations to exhaustive studies, we continuously find proof that high contrast and glare will affect productivity in the workplace.

Not only is bilateral lighting preferred for being more comfortable, but it instinctively feels more natural. Balanced light – light coming from more than one direction – is more akin to ‘natural’ light. In the great outdoors we have both direct sunlight and light from the sky itself – light coming from all different directions. This helps provide depth, giving us clear information about shapes and forms. A strong light source from one direction tends to flatten our views, providing less visual information. Dramatic, but a bit unnatural, and uncomfortable over long periods of time.

Notice how the unlit wall, relative to the illuminated walls on either side,
looks dim and cavernous in contrast with the daylit atrium above.

Since many large or multi-story buildings tend to introduce daylight through sidelighting, it is critical to balance the overall lighting in the space. The more daylight introduced from one side, the more light it will take from the opposite side to offset cavernous effects. Of course, introducing more daylight through an additional window or clerestory is the most effective approach since it will maintain the same exterior intensities. If daylight cannot be provided, supplemental electric lighting should be designed to fill in the gradients where daylight is lowest. Washing walls and surfaces with light and using light colors will increase the perception of balanced light in the space.

The relationship between daylighting apertures and electric lighting is key. There is a lot to be learned from historic, daylit buildings. We should not ignore those patterns throughout the history of great architecture that have always met with positive responses from the humans who use them.

Despite some of their current shortcomings, we are all enamored with the hope and promise of LEDs. When we begin a design session with a client these days, it’s a matter of minutes until someone asks “can we use LEDs for that?!” We respond with the usual overview that there are some very good LED products on the market now, but there are also a lot of poorly-made products, snake-oil sales claims, and companies without a proven track record. In essence, “proceed with caution” is our approach.

One of the things that has bothered me most about LED fixtures is their visual color temperature. The products that I have seen and tested give off a light that is too cool for my preference. But, the world is changing and perhaps my perspective is starting to change a bit too. The following is A Tale of Two Task Lights: a Recently Acquired Fixture and the Lessons Learned.

Good tales often begin with a historic perspective, and so shall this one. Throughout the ages, people have associated low-level lighting with the warmth of firelight or of a candle. I confess that I love the warmer color temperature of a halogen task light. My desk lamps and even the under-cabinet lighting in my kitchen have always been halogen.

The indirect fluorescent lighting that I also have in the kitchen provides a very energy-efficient and comfortable ambient light level in the evenings, but the color does not deliver the same warm glow as the halogen. When the under-cabinet halogen lights are dimmed, they get even warmer and more ‘buttery’. I have yet to achieve that same warm, low light level with LED, compact fluorescent, or linear fluorescent products.

From among the outpouring of new LED products, I purchased my first LED task light this year. I did this to begin to wean myself off of my halogen diet, or at least to try in good faith to live with this new technology. Perhaps it also relates to the overall picture of striving to live healthier and in a more sustainable way. I suppose a parallel could be made with eating healthier – using less butter and more olive oil, for example. Yes, I started to compost as well.

I put my 50-watt, 2850K halogen task light into storage, and began to use my sleek new 9-watt LED desk fixture. The color temperature is specified at 3000K. For the first month or two I had a knee-jerk negative reaction whenever I turned it on. Too cool – as in temperature, not hip factor. I missed that warm buttery glow. However, over the course of a few months, I am beginning to grow accustomed to its cooler cast. The fixture has excellent glare control and the output is comfortable. If the fixture produced glare, or was either too dim or too bright, those factors would have certainly biased me against the LED task light. But I couldn’t find fault with it in those areas.

It has been about six months and I am now acclimated to the light quality of my new task light. I enjoy using it and the color temperature has sort of grown on me. Does making healthy choices involve accommodation and adjusting our standards, or is it the retooling our thinking and attitudes, which open us up to new options?

I believe that, as LEDs become more widespread in offices and homes, retail, street lighting, parking garages, etc. in the next few years, their shortcomings – particularly in the area of color temperature and glare control – will cause a backlash among users. The marvels and mysteries of LEDs as the great hope for our future will be tarnished by products that don’t live up to their promises and our expectations. While I do believe that the industry will have to deal with these shortcomings, what I have learned is that people are surprisingly adaptable to new technologies.

The visual issues that manufacturer’s have been dealing with – glare, multiple shadowing, effective dimming, cooler color temperature, and that strong desire for warmer color temperatures when dimmed – will get worked out over time as we grow accustomed to a new light.

On a recent trip to Thailand, I enjoyed a rare opportunity to experience traditional responses to local design challenges, unique architectural expressions of place. Upon arrival, one of the first things you notice is the very hot tropical climate. Then, as you explore, you start to notice the particular cultural responses to this climate – that there is a recognizable characteristic, developed out of necessity, present throughout regional design traditions.

There is a continuous theme of architectural techniques that respond directly to climate with a simplicity and completeness of expression, especially evident in visits to some of the many magnificent Thai temples.

Approaching the temples, there is a sense of grandeur as bright sun shimmers off of the brightly colored tiles, among an array of sweeping roof structures and light exterior surfaces. The journey of enlightenment begins with this first glimpse of the temple complex, and continues inside with a smooth progression from the bright outdoors, through shady verandas, to serene interiors.

The temples use deep overhangs and verandas to provide vitally important shade, in response to the direct sun and persistent hot weather. These elements mediate the tremendous brightness contrast, while at the same time, acting as a threshold to solemnize the moment of entering the sacred space.

Inside, surfaces are defined by dark wood, in less reflective colors and textures. This transition has a phenomenological effect of coolness, and establishes your focus on the gleaming Buddha that reflects indirect daylight from the windows. The dazzling reflections emanating from golden surfaces are a beautiful visual expression of the Buddha’s spiritual magnitude.

The traditional Thai temples are filled with only a subdued sense of natural daylight, which is an interesting contrast to contemporary thinking, but the dark walls and ceiling are not perceived as blank planes; there is just enough ambient light to pick up ornate, glossy details which define the structure. The effect, though subdued, creates an inspiring, pleasing atmosphere.

During my travels in Thailand, there were many new experiences, but throughout them all, what I enjoyed the most was this collaborative expression of daylight and transition, and the harmony with which the local architectural style transcends necessity.

Continuing on the topic of the well-balanced architectural diet and exploring the parallels between food and design (“In Defense of Design“), I come back to the notion of variety. Because of our very energy-intensive lifestyles, we can virtually have it all. Peaches in the winter, cheap beef year-round, and 72 degrees, 50% relative humidity, and 50 footcandles uniformly distributed throughout every interior space.

It wasn’t that long ago when people actually enjoyed truly seasonal fruits and vegetables, only ate beef and pork in the late fall and winter and chicken in the summer, and went to school in un-air-conditioned buildings. As far as food goes, more people are now turning back to organic or locally grown produce and meats. It’s much more sustainable to buy food that’s grown close to where it is consumed. It takes a lot of energy to fly and truck in peaches from Chile to Boston in January – and they’re really not that tasty… The same goes for our architectural environments.

Architecture started depending more on energy, and less on structure, to solve its environmental issues. It’s become so “processed”, cooled, heated, lighted, that we’ve lost some of the simple drama arising from varying temperatures and light levels.

Wearing a sweater indoors in the wintertime in order to lower the thermostat worked for Jimmy Carter. Better yet, having families gather around the inglenook to keep warm not only saved energy but promoted family conversation. Placing more demanding visual tasks near windows kept valuable illuminants from being exhausted during the hottest times of the day. As far as residential architecture goes, many of these variations are not impractical today. They say the passive solar homeowner is a very tolerant creature. Commercial spaces are somewhat more demanding of environmental power, but certainly not to the intensity common in most buildings today.

Bringing it back to lighting, what’s wrong with a little variation in illuminance levels? When we walk around outdoors, we experience moonlight which is about one one-hundredth of a footcandle, while bright sunshine could be as high as 10,000 footcandles – a difference of a million to one. Walking through dappled patterns of sun and shade can vary in luminance ratios greater than a thousand to one.

And yet, when we design electric lighting for interiors, we must have a certain prescribed level, a “zone”, or people get upset. Darker areas are misconstrued as mistakes: “not enough light”. Not only is it good to vary light levels within an interior environment based on activity, but it’s also good to have various illuminance levels throughout the day. It puts us in touch with our environment and defines a sort of time-space continuum.

When we daylight buildings, we have the opportunity to not only save energy, but to make them wonderful and enlivened. The changing patterns of light and color throughout the day add a dynamic quality. And yet we read technical articles about daylit architecture and how it’s “bad” to have direct sunlight inside the building. It may be less desirable to have it stream across your keyboard, but who doesn’t like a view of sunlight? Doesn’t it seem strange that the daylighting point in LEED is in the Environment and Atmosphere section, a purely qualitative metric, yet we have to reach 25 footcandles in order to get the point, a quantitative measurement? It’s a peach, right? Who cares what it tastes like?

There are clever products on the market that help introduce daylight into spaces that may not normally have it, but sometimes they’re used as crutches, in lieu of good design. “Light-tubes” vs. light wells for instance. When daylight comes out of the other end of a “light-tube” it is completely unrecognizable as daylight. A great dinner combines a range of different and complementary ingredients, enjoyed throughout the duration of the meal. Those ingredients could easily be put into a blender and would yield the same nutritional value. The thought isn’t too appealing unless it’s a smoothie we crave. If we let codes and standards dictate the way daylight is introduced into architecture by some formula or prescription, all of the nuances and beauty of daylight could be lost in the name of saving energy.

California has requirements now that any interior space directly below a roof must be skylit. Generally this is a good idea. However, it also states that the skylight glazing must be translucent – crazy. Therefore we are benefitting only from the light energy it provides, and little else. A beautifully executed clerestory or redirected sunlight would not qualify. Where have we gone wrong?

When it comes to a quality meal, should we evaluate it based on calories per dollar? This may be the very idea behind an all-you-can-eat buffet. Should daylight simply be evaluated on number of footcandles at certain times of the year? If you only drink your wine from a box, don’t answer this last question.

Brightness, color, and contrast all play a role in any visual composition. This is especially true of lighted nighttime environments; the interplay of these three characteristics determines the quality and character of the lighted environment.

In the foreground of this image, on the right-hand side, is a brightly lighted mock-up of what is soon to be a prominent architectural feature of a new high-rise building under construction in Boston. The color-changing LED fixtures seen at the bottom of the image will highlight this building feature at different intervals, adding a playful element to the Boston skyline at night. The property owners will determine which colors to accent this element with, and therefore can control how subtle or dynamic this feature for different occasions. The use of color helps distinguish this lighted portion of the building from the sea of white light spilling from the windows of surrounding buildings in the skyline.

The overall brightness can be adjusted by dimming the LED fixtures. In the middle of the night, when most are asleep, the brightness can be reduced by dimming, giving a more subtle appearance than what might be desired earlier in the evening during prime viewing hours.

The contrast within a photograph taken shortly after dusk often produces the most striking images of lighted environments. The deep color of the sky enlivens the image, while it is the contrast between the sky glow and the dark silhouettes of buildings that defines the city skyline. A few minutes later in the day, and the sky will be too dark, the contrast is reduced, and the perception of the building forms is lost.

As designers we never want to use color or increase brightness just for the sake of doing so; more is not necessarily better. However, all of the lighted environments that we design must balance these characteristics – brightness, color, and contrast – and use them carefully to hopefully create architectural projects that become stunning images.

How does one successfully photograph a piece of architecture? Do you need the widest lens available to capture as much as possible? Or the latest and most expensive digital equipment to produce the sharpest images? Sure, it helps to have the right equipment, but that is just the start.

Any successful architectural photograph should articulate and balance three key elements: form, color, and movement.

The forms being photographed define the composition of the image. The edge of a building, a row of windows, a pattern in the floor tiles… in 2D these elements are transformed into visual cues that draw our eyes around the image.

How the forms in an image are communicated to the viewer is enhanced by varying intensities of color, which in turn arise through variation in light quality and intensity. Brighter portions of an image bring out and enhance the shadows and silhouettes that occur elsewhere in the scene. Areas of contrasting light and darkness create interest and keep an image from looking gloomy or monotonous.

Dusk is the “magic hour” for taking pictures. As the sun sets below the horizon, the sky turns a rich shade of blue, clouds are transformed in orange and pink, and the colors of objects suddenly come alive. Under full sunlight, colors are washed out, but at dusk they become fully saturated and fascinating. Light from various directions begins to come into play as the daylight dims down and the electric lights come on. Well-placed lighting can reveal interesting details of architecture that go unnoticed in the daytime, and create hierarchy and structure in an image.

Movement can be anything that gives the impression of direction or fluidity. This could be, for instance, a curving wall that leads your eye across the image, or it can be something actually moving, like the trees in this image, which are blurred by the wind and the shutter delay of the camera. This tension between static and dymanic elements is often what makes an image breathe.

In this photograph, taken out on the second-floor terrace of the new Northeastern University dormitory, we pulled all these elements together to try and convey our work on the lighting design. The glow below the bench and the grain of the floorboards draw the eye diagonally into the scene to the multi-story lobby space beyond. The bright downlights and white ceilings form a smooth vertical element that eventually breaks the border of the image. A pattern of regular square windows beyond are accented by spill light catching the edges, giving depth to the saturated deep-orange façade. The deep blue sky in the corner provides a splash of complementary color. Windswept trees, lit from below in the planter beds sway gently, and the faceless person sitting on the bench gives the terrace a purpose.

GKD Metal Fabrics is a manufacturer of interwoven metal meshes for large-scale architectural use. They have a great website with lots of project images that really show off the visual effects possible with woven or perforated surfaces.

Woven metal fabrics offer a wonderful visual inversion: when the primary illumination is on the viewer’s side, the surface appears solid. When the illumination is on objects or wall surfaces behind the fabric, the fabric appears transparent and, when viewed from a distance, can almost completely disappear.

This is very much the same effect as that of a theatrical scrim: when light in front of the scrim fades down, and light on the scene behind the scrim is increased, the scene is “magically” revealed.

However, many designers don’t understand this concept and mistakenly try to backlight the metal mesh (or perforated metal panel, which is the same effect) in an attempt to make it “glow”. If you backlight a perforated solid object, there is no material to reflect, refract, or diffuse the light, so it looks dark even though lots of light might be streaming through the openings. At most, you might catch a little of the light on the lip of the openings if the material is thick enough, but this is generally not the intended effect.

Light cannot diffuse through solid metal like it can through translucent glass or plastics. To create the impression of gauzy transparency with metal products, the surface must be mostly open (more like woven fabric rather than perforated panels) and the light on the front of the scrim must be approximately the same as the light on whatever is behind the surface.

Beyond a neat visual effect, metal mesh offers an intriguing way to control solar load and excessive daylight penetration, while helping a building take on a dynamic visual persona that changes from day to night.